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An OCF Dipole with Homebrew 4:1 Balun

Created by Greg Danes, KJ4DGE on 2019-10-16

An OCF Dipole with Homebrew 4:1 Balun
By KJ4DGE

In keeping with experimentation and costs down I recently embarked on trying to make a dual band 17/10 dipole with limited results. Either it was resonant on 17 or 10 but never both. I decided why if using the FT-990 with tuner should I limit myself to 2 bands? My next thought was an 80 through 10 OCF. The main thing here was to have a tunable, low SWR antenna that would work all bands of HF without traps, excessive length and at the same time allow me some fun to experiment.

In keeping with experimentation and costs down I recently embarked on trying to make a dual band 17/10 dipole with limited results. Either it was resonant on 17 or 10 but never both. I decided why if using the FT-990 with tuner should I limit myself to 2 bands? My next thought was an 80 through 10 OCF. The main thing here was to have a tunable, low SWR antenna that would work all bands of HF without traps, excessive length and at the same time allow me some fun to experiment.

I spent 21.00 on 100 ft. of 14 gauge copper stranded antenna wire from Universal Radio. I measured out a 41 then a 25 foot section. Next I took a 1 lb plastic coffee can lid as the separator for the dipole and hookup point for the coax. I used a heavy thick glass spice jar as the insulator as the plastic lid is solid and drilled a hole into it to slip and tie a knot in the copper wire before putting the lid back on.

The dogbone was later replaced by another spice jar done the same way. Having hoisted this into the trees using a 18 foot bamboo pole I began testing. First off it was Ok with a 2:1 SWR on SOME of the bands. I realized what was needed was a 4:1 balun but the idea of spend anywhere from 30-60 dollars for one was not in the cards so I searched YouTube for "Homebrew 4:1 antenna balun" and found this.

https://youtu.be/7lYY7nkKrWo

I could not find a adequate piece of 1 inch PVC pipe so cut a 1 inch piece of bamboo to use. After sketching out the directions on paper to go by I made the balun and put it at the base of this odd looking thing. Testing for SWR on the bands again at 10 watts for a load I found that I now could tune the entire band with the highest SWR being on a portion of the lower 20 meters being no more than 1:2:1!

Next was to listen up at 10 meters which from my QTH has been a wasteland of signals. I not only copied a weak SSB QSO but now could hear CW and signals all the way down to 11 meters. The other bands of 12, 15 and 17 also were devoid of anything due to propagation woes but no doubt being able to tune these now will add to the fun as things improve. Also the orientation is N-S which has allowed me to work into Florida and Georgia these last couple days with a S-8 to 9 signal report and it's a very quiet antenna as well.

The homebrew 4:1 balun was the key in all this. Surprisingly it will tune up on 80 meters but since I have a bigger antenna for that band I choose not to go there with this one.

Total cost of this multi-band antenna was 21.00 for the wire and about 4 hours of work putting it together with testing.

There is a great deal of satisfaction making something that works made from what you have lying around.

Best DX
De KJ4DGE

KJ4DGE 2019-11-01
Re: An OCF Dipole with Homebrew 4:1 Balun
Has survived current 50 mph winds, rain and such reinforced at time of being built with Gorilla tape. Going on 4 months now :)
KJ4DGE 2019-10-30
Re: An OCF Dipole with Homebrew 4:1 Balun
8 weeks and still in one piece, hail the power of Gorilla tape!
KB5ITJ 2019-10-29
An OCF Dipole with Homebrew 4:1 Balun
Have used an OCF dipole for about 10 years, SWR between is 1.1 to 1.5 across 4 bands . It's the best antenna for the money and easy to build. (my opinion) Have build them from scratch using junk parts and small gauge wire for temporary use, always worked well. My current setup is a 10 thru 40 OCF and a Hustler 4BTV vertical, hoping to put up a 10 thru 80 OCF as soon as I can trim some trees.
KJ4DGE 2019-10-28
Re: An OCF Dipole with Homebrew 4:1 Balun
2 months in high wind and still in one piece, love that Gorilla tape! :)
W4HM 2019-10-27
An OCF Dipole with Homebrew 4:1 Balun
A really high quality BALUN is needed to really make an OCF dipole operate properly. Without one the common made current (CMC) can really mess up where the antenna is resonant.

I had to take a really high quality and pricey commercial BALUN and still add a CMC coax choke after the BALUN for the antenna resonate properly.
Check out this web page at http://www.dj0ip.de/off-center-fed-dipole .
W9IQ 2019-10-25
Re: An OCF Dipole with Homebrew 4:1 Balun
As Dale mentioned, the device depicted in the YouTube video is not a balun. A 4:1 (or 1:4) balun requires two ferrite cores. The device pictured is more properly called an unun. It is essentially an autotransformer. This type of device can perform the desired impedance transformation but it will not help in suppressing common mode current.

An OCF dipole tends to promotes the formation of common mode current due to its inherent imbalance (the different lengths of the legs). This will generally cause the coax to become part of the radiating and receiving antenna affecting the antenna pattern and potentially picking up local RFI during receive.

The use of a proper 1:1 balun between the unun and the coax will help to reduce common mode current. This, of course, adds weight to the center feedpoint of the antenna. But the core count for a proper 4:1 balun is the essentially the same since two cores are required.

- Glenn W9IQ
W4OP 2019-10-23
RE: An OCF Dipole with Homebrew 4:1 Balun
Agreed, and if I were a zoologist I would have an extensive knowledge of wolves.
Ergo, if I am into antennas I should know the theory of baluns and ununs. But if you ask 100 hams what the function of these devices is, 99 will tell you it is for improving SWR

Regards,


Dale W4OP
VE3KKQ 2019-10-23
RE: An OCF Dipole with Homebrew 4:1 Balun
Because those who have nothing but vile in their comments have nothing pertinent to contribute to any subject. In other words they are envious that the author has knowledge, skills and the imagination to try something that they don't thus, they feel inferior and less accomplished.
KJ4DGE 2019-10-23
RE: An OCF Dipole with Homebrew 4:1 Balun
Yes Baluns and Ununs are grossly misunderstood, then so are wolves...
K9FV 2019-10-21
RE: An OCF Dipole with Homebrew 4:1 Balun
KJ4DGE, You certainly have the experience to build things "high tech". Something lot of folks seem to have missed, your article was for a "quick 'n dirty" all band antenna, and it works! Well, except perhaps for your "balun", and it did seem to lower the SWR. I saw the list of downloads from your google drive and will be exploring those.

Thanks for the article,
73 de Ken H> K9FV
WB4M 2019-10-20
An OCF Dipole with Homebrew 4:1 Balun
I agree that it is fun to make an antenna that works out of material that is just laying around. Yes you could have used better insulator, etc, but you didn't have one so you improvised. Over the years I have saved old antenna parts for this purpose. When I ditched my satellite TV, the pole the dish was mounted on made a great mount for a 30 meter vertical. I have a lot of junk in my shed that I'll probably never use but I view everything for possible future use for antenna building.
KB4MNG 2019-10-20
An OCF Dipole with Homebrew 4:1 Balun
This is saving money at it's worst. Just not a good overall set up.

kb4mng
KUS335983 2019-10-19
RE: An OCF Dipole with Homebrew 4:1 Balun
N0ETR hit it right on the head! Too many alpha hotels out there that wouldn't have the stones to be as negative to anyone's face as they do in the safety of their little virtual worlds.
KUS335983 2019-10-19
An OCF Dipole with Homebrew 4:1 Balun
LOVE THIS!!

Creative, cost-effective, and capable! Forget the negativity: it's a great experimental antenna. THANK YOU for sharing.

W4OP 2019-10-18
RE: An OCF Dipole with Homebrew 4:1 Balun
Hi Greg,
Thank you for the kind words. My comment was not on the antenna or the materials you used to make the antenna. I am all in favor of hams building their own equipment and we all learn in that process what works, what lasts and what does not work.
Testing and comparing antennas is very difficult at HF.
Today we are fortunate to have NEC engines that get us very close to the real world. All of my commercial antenna clients now readily accept NEC models.

So, my comment was on the 4:1 balun. Balun and Unun are very much misunderstood today. Most of what you see on the market are transformers or voltage baluns-which without a 1:1 choke following the transformer or voltage balun do not suppress common mode currents. That is the primary purpose of a Balun. I am not all that concerned about the pattern of my 40,80 and 160M dipoles, but I do not want noise in the shack being transported out to my antennas (via common mode) and then that noise coming back to my rig via differential or transmission line mode. My antennas are far from the house, but without a proper balun, I would be hearing all sorts of house noise on those antennas.

One certainly cannot depend on YouTube for accurate information on baluns- 99 out of 100 only look at SWR with no clue as to whether the device is perfoming its primary function.

I guess it is the engineer in me that instead of saying "it works" says "how can I make it better?
Thank you for your article and responses. And I am a bit jealous you got to work at Heath. What a great experience that must have been.

73,
Dale W4OP
KJ4DGE 2019-10-18
RE: An OCF Dipole with Homebrew 4:1 Balun
Dale,
W4OP
Having read your QRZ page I am impressed to all get out with your prowess as a home-brewer. I am also one that worked at one of the best and most technically educational places around. HEATHKIT. I was not a designer of kits at St. Joseph, I was a tech who fixed the kits that folks messed up. I had NO experience when I started working there but someone saw I had savvy for repairs and hired me. To design something from scratch and build it as you do impresses the heck out of me. Pointing out my errors is also OK with me but why change something or tweak it if it works? Yes it might make it better or less prone to something but then I have less time to enjoy it perhaps....

Still I appreciate your input and all the others who commented as well. There are designers, engineers, tinkerers, and repair guys in the HAM radio hobby. I guess all together we do what we do for it, (the HOBBY) and others expand or learn from it in various ways.

Peace
KJ4DGE
W4OP 2019-10-17
RE: An OCF Dipole with Homebrew 4:1 Balun
So, it is not proper to point out a technical error that when remedied would likely result in the outer shield of the feedline no longer being part of the antenna- leading to more noise on RX, possible RFI etc? i.e. a better antenna.
If the choking impedance of the so called balun is not known then how can one judge if it is functioning as a blaun/unun? Certainly SWR gives no clue. The primary purpose of baluns and ununs is to prevent common mode radiation.
But because CMRR is a little more difficult to measure- few do it.
This is, or used to be a technical hobby and elmering was sought out.

Dale W4OP
N0ETR 2019-10-17
An OCF Dipole with Homebrew 4:1 Balun
Does anyone ever stop to think that there may be some non-ham people looking at the reply's to this article? If I were a non-ham I would stay as far away from ham radio as possible after reading them. Gone are they days
home brewing on a budget and just having fun sharing your ideas. Too many non-constructive critics out there.
Get a life people. It's a hobby.
K4PIH 2019-10-17
An OCF Dipole with Homebrew 4:1 Balun
I've been to Greg's QTH and I can tell you he can make something out of nothing! No credit card ham here, a real builder. I think I'll refine the materials a little and put one up at my QTH before the cold sets in.

Thanks Greg, keep experimenting.

73
KT4ZE 2019-10-17
An OCF Dipole with Homebrew 4:1 Balun
Nice! Always rewarding when something works. Thanks for taking the time to do the project and letting us know about it!
KJ4DGE 2019-10-17
RE: An OCF Dipole with Homebrew 4:1 Balun
Its still standing after 4 months along with all the other antennas I have built, not pretty, maybe not scientific enough but they work and as stated they are fun to make. I have no engineering degree, never took a class to work at Heathkit for 10 years nor make service manager, just passion for something. Try/fail then try again until perhaps you get to point you want.

Life is a lot like that perhaps...
K8QV 2019-10-17
An OCF Dipole with Homebrew 4:1 Balun
Why is everyone being so rough on this guy? It's not presented as the ultimate antenna, it's just fun to make something that works from the crap lying around the house. Remember fun?
W4OP 2019-10-16
An OCF Dipole with Homebrew 4:1 Balun
The device is a 4:1 transformer not a balun. The common mode impedance of the device, if any is unknown. The terms balun and unun are likely the most misused term today.
Dale W4OP
KJ4RWH 2019-10-16
RE: An OCF Dipole with Homebrew 4:1 Balun
I once made an antenna system of paper mache`. It burst into flame during a lengthy rag chew. The coffee can lid and glass spice bottles would be an upgrade for me. Has anyone tried a KFC bucket?
KC0W 2019-10-16
An OCF Dipole with Homebrew 4:1 Balun
I give the plastic coffee can lid 2 weeks at most.........Nothing wrong with saving money but I prefer to do things right the first time so I don't have to do it second time.

Tom KH0/KC0W